Insights into the Pathobiology of TMPRSS3-Related Hearing Loss and Implications for Cochlear Implant Patients with TMPRSS3 Mutations.

OBJECTIVES To review the audiological outcomes after cochlear implantation (CI) for TMPRSS3-associated autosomal recessive non-syndromic hearing loss (ARNSHL) and evaluate the spatial expression pattern of TMPRSS3 within the human cochlea. METHODS Review all published cases of CI in patients with TMPRSS3-associated ARNSHL to compare postoperative consonant-nucleus-consonant (CNC) word performance to published adult CI cohorts. Protein structural modeling of TMPRSS3 variants associated with post-lingual hearing loss. Determine TMPRSS3 expression pattern in human inner ear organoids and human cochlea. RESULTS Nine articles detailed 27 patients (30 total CI ears) with TMPRSS3-associated hearing loss treated with CI. Of these, 6 cases reported prelingual onset (< 2yo) and 24 cases reported post-lingual onset (≥2yo) of hearing loss. Subjectively, 85% of cases had a favorable outcome. Objectively, the postoperative mean (SD) post-operative CNC word score was not significantly different than other adults [66.2% (25.8%) correct vs. 50.1% (12.5%); F(1,6) = 1.97, P = 0.21]. In the TMPRSS3 cohort, poor performers (CNC < 30% correct) were significantly older than good performers [49 (± 13.3) years vs. 17.4 (± 18.4) years; P < 0.01] and all harbored the A138E variant. TMPRSS3 immunostaining is restricted to the otic epithelial cells and is not expressed within auditory neurons of human cochlea and human inner ear organoids. CONCLUSIONS Patients with TMPRSS3-related hearing loss exhibit similar postoperative performance to other adult CI patients. TMPRSS3 is not expressed in human auditory neurons and the duration of hearing loss prior to CI likely contributes to poor performance.

Spatial Expression Pattern of the Major Ca2+-Buffer Proteins in Mouse Retinal Ganglion Cells

The most prevalent Ca2+-buffer proteins (CaBPs: parvalbumin—PV; calbindin—CaB; calretinin—CaR) are widely expressed by various neurons throughout the brain, including the retinal ganglion cells (RGCs). Even though their retinal expression has been extensively studied, a coherent assessment of topographical variations is missing. To examine this, we performed immunohistochemistry (IHC) in mouse retinas. We found variability in the expression levels and cell numbers for CaR, with stronger and more numerous labels in the dorso-central area. CaBP+ cells contributed to RGCs with all soma sizes, indicating heterogeneity. We separated four to nine RGC clusters in each area based on expression levels and soma sizes. Besides the overall high variety in cluster number and size, the peripheral half of the temporal retina showed the greatest cluster number, indicating a better separation of RGC subtypes there. Multiple labels showed that 39% of the RGCs showed positivity for a single CaBP, 30% expressed two CaBPs, 25% showed no CaBP expression, and 6% expressed all three proteins. Finally, we observed an inverse relation between CaB and CaR expression levels in CaB/CaR dual- and CaB/CaR/PV triple-labeled RGCs, suggesting a mutual complementary function.

Spatial Expression Pattern of the Major Ca2+-buffer Proteins in the Mouse Retinal Ganglion Cells

The most prevalent Ca2+-buffer proteins (CaBPs: parvalbumin&mdash;PV; calbindin&mdash;CaB; calretinin&mdash;CaR) are widely expressed by various neurons throughout the brain, including the retinal ganglion cells (RGCs). Even though their retinal expression has been extensively studied, a coherent assessment of topographical variations is missing. To examine this, we performed immunohistochemistry (IHC) in the mouse retina. We found variability in the expression levels and cell numbers for CaR, with stronger and more numerous labels in the dorso-central area. CaBP+ cells contributed to RGCs with all soma sizes, indicating heterogeneity. We separated 4-9 RGC clusters in each area based on expression levels and soma sizes. Besides the overall high variety in cluster number and size, the peripheral half of the temporal retina showed the greatest cluster number, indicating a better separation of RGC subtypes there. Multiple labels showed that 39% of the RGCs showed positivity for a single CaBP, 30% expressed two CaBPs, 25% showed no CaBP expression and 6% expressed all three proteins. Finally, we observed an inverse relation between CaB and CaR expression levels in CaB/CaR dually- and CaB/CaR/PV triple labeled RGCs, suggesting a mutual complementary function.

A polarized nucleus-cytoskeleton-ECM connection controls collective migration and cardioblasts number in Drosophila

The formation of the cardiac tube is a remarkable example of complex morphogenetic process conserved from invertebrates to humans. It involves coordinated collective migration of contralateral rows of cardiac cells. The molecular processes underlying the specification of cardioblasts prior to migration are well established and significant advances have been made in understanding the process of lumen formation. However, the mechanisms of collective cardiac cells migration remain elusive. Here we identified CAP and MSP-300 as novel actors involved in cardioblast migration. They both display highly similar temporal and spatial expression pattern in migrating cardiac cells and are required for the correct number, alignment and coordinated directional migration of cardioblasts. Our data suggest that CAP and MSP-300 are part of a tension-sensitive protein complex linking cardioblast focal adhesion sites to nuclei via actin cytoskeleton and triggering coordinated cardioblast movements.

Statistical Analysis of Spatial Expression Pattern for Spatially Resolved Transcriptomic Studies

ABSTRACTRecent development of various spatially resolved transcriptomic techniques has enabled gene expression profiling on complex tissues with spatial localization information. Identifying genes that display spatial expression pattern in these studies is an important first step towards characterizing the spatial transcriptomic landscape. Detecting spatially expressed genes requires the development of statistical methods that can properly model spatial count data, provide effective type I error control, have sufficient statistical power, and are computationally efficient. Here, we developed such a method, SPARK. SPARK directly models count data generated from various spatial resolved transcriptomic techniques through generalized linear spatial models. With a new efficient penalized quasi-likelihood based algorithm, SPARK is scalable to data sets with tens of thousands of genes measured on tens of thousands of samples. Importantly, SPARK relies on newly developed statistical formulas for hypothesis testing, producing well-calibrated p-values and yielding high statistical power. We illustrate the benefits of SPARK through extensive simulations and in-depth analysis of four published spatially resolved transcriptomic data sets. In the real data applications, SPARK is up to ten times more powerful than existing approaches. The high power of SPARK allows us to identify new genes and pathways that reveal new biology in the data that otherwise cannot be revealed by existing approaches.

Transsynaptic interactions between IgSF proteins DIP-α and Dpr10 are required for motor neuron targeting specificity

The Drosophila larval neuromuscular system provides an ideal context in which to study synaptic partner choice, because it contains a small number of pre- and postsynaptic cells connected in an invariant pattern. The discovery of interactions between two subfamilies of IgSF cell surface proteins, the Dprs and the DIPs, provided new candidates for cellular labels controlling synaptic specificity. Here we show that DIP-α is expressed by two identified motor neurons, while its binding partner Dpr10 is expressed by postsynaptic muscle targets. Removal of either DIP-α or Dpr10 results in loss of specific axonal branches and NMJs formed by one motor neuron, MNISN-1s, while other branches of the MNISN-1s axon develop normally. The temporal and spatial expression pattern of dpr10 correlates with muscle innervation by MNISN-1s during embryonic development. We propose a model whereby DIP-α and Dpr10 on opposing synaptic partners interact with each other to generate proper motor neuron connectivity.

Transsynaptic interactions between IgSF proteins DIP-α and Dpr10 are required for motor neuron targeting specificity in Drosophila

ABSTRACTThe Drosophila larval neuromuscular system provides an ideal context in which to study synaptic partner choice, because it contains a small number of pre- and postsynaptic cells connected in an invariant pattern. The discovery of interactions between two subfamilies of IgSF cell surface proteins, the Dprs and the DIPs, provided new candidates for cellular labels controlling synaptic specificity. Here we show that DIP-α is expressed by two identified motor neurons, while its binding partner Dpr10 is expressed by postsynaptic muscle targets. Removal of either DIP-α or Dpr10 results in loss of specific axonal branches and NMJs formed by one motor neuron, MNISN-1s, while other branches of the MNISN-1s axon develop normally. The temporal and spatial expression pattern of dpr10 correlates with muscle innervation by MNISN-1s during embryonic development. We propose a model whereby DIP-α and Dpr10 on opposing synaptic partners interact with each other to generate proper motor neuron connectivity.